Electrical indicator



t e e h S .w Dv e h s 2 Y. L L E Nv N E K B Aw u d 0 M O m ELECTRICAL INDICATOR.

vlAsnmuron, o. e.

(No Modelff 2 sneetssheez. 2. E. KENNELLY.

TRIGAL INDICATOR.

, N9.; 517,163? Patent-ed Mar. 27,1894.

YTAtrEs ATENT Erice.

ARTHUR E. KENNELLY, OE ORANGE, AssiGNOR To THOMAS A. EDisON, OF

' LLEwELLYN PARK, NEw JERSEY.Y

ELECTRICAL INDICATOR.

sPEcrFicAcrroN forming pare of :Letters Patent No. 517,163, asesinaron 27, 1894.

To al? whom it may concern: I

Be it known that I, ARTHUR E. KENNELLY, a subgect of theQueen of Great Britain, re-

f'siding at Orange, in the county of Essex and State of N ewJ ersey, have invented a certain new and useful Improvement in Electrical Indicators, ofwhich the following is a specification.

The present invention relates to electrical measuring or indicating devices of that class employing amagnet of constant strength, between the poles of which is a pivoted armature controlling a pointer movable over a graduated scale.

The main object of thc invention is to improve the construction of instruments of the character indicated, whereby increased siniplicity and more perfect operation are secured, and the invention consists in the several features and combinations hereinafter more fully described and specifically set forth 1n the claims. e

In the accompanying drawings illustrating the invention, Figure 1 is a plan view of the instrument with its cover removed. Fig. 2 is a seoti on on line --x of Fig. 1,looking in the direction of the arrow. Fig.3 is a detail view illustrating the construction and winding of the armature, (which winding is omitted in F1g.2 to avoid confusion of linesg) and Fig. 4. shows a modification.

The permanent magnet 1, preferably employed, is of horseshoe orcurved form, having ends nearly meeting at one side as shown 1n Fig. To the ends of this permanent magnet are secured wrought iron pole pieces 2, 3, by means of screws 4. These pole pieces preferably terminate in rounded ends 5, which ends are considerably thinner than the main portion of the pole pieces, as shown in Fig. 2. Each pole piece is preferably cut away at 6 to make room for the spindle and hub of the armature, as most clearly shown in Fig. 2.

7 is a non-magnetic bar secured to the permanent magnet and forminga support for the plate 8 which supports the bearing 9 for the spindle 10 and the insulated plate 11, which carries an arm 1 2, to which a light coil spring 13 is connected, the opposite end of said coil being connected to the spindle in such manner as to tend to turn the pointer 14. to zero.

' Application iiled October '26, 1892. Serial No. 450,063. (No model.)

13 is a'second spring co-operating with the first and supported, in the manner indicated in the drawings, so as to be insulated from the spindle.

15 is a small counterbalance weight.

The armature is a thin disk armature, and preferably consists of an aluminium disk 16, to the periphery of which is secured a rubber ring 17, having a groove around it, and having notches 18 at intervals on one side, and at one point having a wider notch 19 to receive the wire of the armature winding as hereinafter described. At the center the disk 16 is stamped into cup form, forming a hub 20 which rests on the sleeve 21 on the spindle.

The preferred mode of winding the disk armature is indicated in Fig. 3. Starting from the point 22` an insulated wire is led radially across the upper face of the aluminiuni disk, being bent down into, and around the center of, the hub 20, then radially along the surface of the plate to the diametrical notch 18, then around toward the right in the groove of the ring to the notch 19, then again across the face of the disk'to said notch 18, then around in the groove of the ring toward the left, thus giving a differential winding on the periphery; the winding then extends to the next notch 18, and so on until there are radial wires extending to each of the notches around the periphery of the ring. The.end 22 is connected to the spindle and thence to the plate 11, as indicated in Fig. 2,.while the other end 23 is connected to the spring 13', insulated from the spindle by the sleeve 2l. -l-, are the line terminals of the instrument and are connected by means of a wire 25 including a resistance 26, which is, for convenience, wound directly on the body of the permanentmagnet, From the same terminal a wire 27 extends to the insulated plate 11, thence through the armature coil and wire 23 to spring 13', thence to 23'; to the terminal, thus completing the circuit of the instru ment. The armature winding described gives a considerable number of wires extending from the notch 19 to the center'of the disk, and in order that the armature may be perfectly balanced, tle counterbalance 15 is placed opposite to said notch; This collection of wires on the armature surface is so located IOC as to be outside of the magnetic field between the facing, overlapping, magnet poles, and preferably normally stands directly in line with the pointer 14 as indicated in Fig. 1. By bending the Wire down into the hub 2O as described it is held in place without special fastenings, and without forming a thick portion which might interfere with the movement of the armature in its thin field between the magnet poles. It will thus he seen that the winding consists of a series of radii in all of which the current flows either to or from the center. Supposing the latter case, the arrangement approximates to a plane current sheet spreading uniformly from center to edge of the disk, except at the radial portion 19 which is never allowed to enter the field, and which allows the current turns to pass back from the edge to the center of the disk. Since the two opposite polar faces are semi-circular, they can only cover one half of the surface of the disk, and the radial section 19 occupies some position in the unoccupied semicircle. When current is supplied to the disk winding, all the radii between the poles will aid in setting up a rotatory couple tending to move the disk round its axis either to the right or left. As the disk turns, as many active wires enter the field at one side as leave it on the other, so that the rotatory couple remains constant so long as the notch 19 does not approach the field too closely. Of the half revolution that is ideally permissible to give the disk without bringing the notch 19 between the poles, it is practically convenient to utilize one hundred and twenty or one hundred and thirty degrees, and with this arrangement the distance between the section 19 and the pole faces is never so small as to seriously affect the uniformity of the rotatoiy couple. The active wires carried round the periphery of the disk, as for example from the notch marked 18 in Fig. 4 to that marked 19, are all outside the circle of the pole faces, and by carrying the wires round in alternately opposite directions, any stray field passing them exerts no appreciable resultant magnetic in uence. When the circuit of the instrument is closed, the armature w ill give a steady, uniform pull, depending on the current on the line, for all positions, so that the scale 2S can be divided into divisions of regular length and calibrated by a single trial. Owing to the form of the armature, the poles of the magnet can be quite large and can be brought very close together, thereby largely reducing the magnetic resistance of the air gap, and making the operation of the instrument much more efcient and regular than with any other form of armature, and the armature pointer can be mounted so as to be capable of movement through a longer arc than heretofore practicable.

In practice the scale can be made one hundred and twenty degrees or more, thereby making it possible to use large divisions on the scale. Then the circuit through the instrument is broken, the pointer will gradually be returned to zero by means of the springs 13, 13. Theinstrument will bedead-beat, since currents will be generated in the metaldisk, forming the body of the armature, tending to oppose sudden movements thereof. The armature described gives a continuous rotary effect with no other appreciable component, such as a side strain on its bearing, and hence the instrument gives very perfect results.

In setting up the instrument, the armature is putin position before the pole piece 2 is secured to the magnet. Said pole piece 1s then put in place, and the steel magnet mag netized by means of a suitable coil or otherwise.

While the instrument has been above described in relation to its use as an ammeter, it can obviously be used as a volt meter. This would generally require the use of a resistance coil in the main circuit, and preferably tlie omission of the shunt. The lwinding of the armature can also be varied to some extent. There need not necessarily be two wires in each armature notch, although there will be two or more when the winding has many turns. The differential condition will not be materially affected if one wire only be led to each notch, as shown in Fi". 4, provided that the returns to the entrance notch 19 are successively carried in opposite directions. It may not always be desirable to enter the first radial wire on the disk exactly opposite to the large notch 19, as the differential arrangement will generallybe more effectively carried out by commencing at some other radius, as indicated at 'r Fig. 4. This is for the reason that the differential balance cannot be perfect everywhere around the periphery, and it is desirable to make it strictly correct for full load.

What I claim is- 1. The combination, in an electrical indicator, of a magnet, a disk armature situated flatwise between the poles of said magnet and having a winding adapted to carry the current to be measured, and an indicating device moved by said disk armature, substantially as described.

2. The combination, in an electrical indicator, of a permanent magnet having extended pole pieces facing each other in close proxim ity, a disk armature situated flatwise in the narrow space between said pole pieces, the coil or winding of such armature being connected to the terminals of the meter and adapted to carry the current to be measured, and an indicating device moved by said disk armature, substantially as described.

3. The combination,inan electricalindicator, of a horseshoe or approximately circular magnet having overlapping pole pieces, an armature situated fiatwise in the space between the overlapping pole pieces, said armature having a coil adapted to carry the cur- IOC IIO

v:517,163 Y e rent to be measured, and an indicati-ng device movable with thearmatu re, substantially as described. A

4. The combination, in an electrical indicator, of a magnet having facing pole pieces, an armature consisting of a non-magnetic disk and a coil extending radially across the face of the disk and around the periphery thereof alternately in opposite directions in the manner described, and connected to terminals of the meter.

5. An armature consisting of a suitable disk or body, and a Winding extending radially across the same and around the edge in one direction, then again across the same and around the edge in the opposite direction, and so on until the winding is complete, substantially as described.

6. An armature consisting ofanou-magnetic disk, a ring around the periphery of the same, and a winding extending across the face of thev disk and around the ring alternately in opposite directions in the manner described.

7. The combination, in an armature, of the disk 16, the insulating ring 17 with notches at intervals, and the Winding crossing the face of the disk and extending around the same from the notches alternately in opposite directions as described.

8. The combination with the magnet, of the disk armature situated iatwise between the poles of said magnet and having a winding extending radially from center to periphery, then round the periphery to a common radial sector over which return is made to the center, the said sector of return being so situated as never to enter the magnetic tield Within the range of the disks mot-ion, substantially as set forth.

This specification signed and witnessed this 17th day of October, 1892.

A. E. KENNELLY.

Witnesses:

JOHN F. RANDOLPH, HARRY F. MILLER. 

